Levels are conventionally used by carpenters and other workmen to determine level and plumb surfaces and some forms of levels are provided with protractor arms and thus may be used as squares and protractors.
However, the spirit vials of some levels shift so as to be improperly calibrated and continued use of protractor arm equipped levels often results in the protractor arms thereof not being properly calibrated to define 90.degree. angles.
Accordingly, a need exists for a level of the spirit vial equipped type and wherein the spirit vials are supported from a level in a manner such that they may be calibrated, if required. In addition, a need further exists for a protractor arm equipped type of level wherein the 90.degree. position of the protractor arm may be calibrated, when required.
Examples of various different forms of levels including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 513,183, 596,818, 602,524, 1,026,967, 1,037,155, 1,260,299, 1,306,722, 1,440,284, 1,920,892 and 2,770,889.